Ultrasonographic evaluation of cross-sectional area of tarsal ligaments in Standardbred Trotter Horses

Ultrasound evaluations of the cross-sectional area (CSA) in the tarsal region of Standardbred Trotter Horses (STH) have been previously reported for tendons but not for ligaments. The objective of this study was to identify normal ultrasonographic CSAs in the tarsal ligaments of STH. Transverse echographic scans of ligaments at five tarsal levels from proximal to distal direction were recorded in 25 healthy STH. All images were recorded, and the CSA measurements (mean +/- SD) were determined. The widest structure resulted in the long plantar ligament (LPL) at distal portion of the astragalus, and the smallest was the long medial collateral ligament (LMCL) at the medial malleolus of the tibia. Long collateral ligaments (LCL) increased their CSA at the level of their distal insertions, while LPL reached the maximum CSA in the middle of its length. Although this report was limited due to its retrospective design, it is the opinion of the authors that the normal CSAs investigated in this paper could function as a reference guide when tarsal pathological conditions are suspected in STH.